They are demanding a new charter to safeguard the rights of Labour's 385,000 members, after complaints that the "Millbank Tendency" has ridden roughshod over their wishes.
The Labour Reform group, one of the biggest inside the party, also wants protection for "whistleblowers" speaking out over internal party elections. It wants polls externally supervised, making elections "genuinely independent of the full-time party apparatus".
The call follows allegations that Millbank officials were aware of the likely election outcomes during voting at elections for Labour's ruling National Executive Committee and the Welsh Assembly.
Mr Blair relied on the votes of trade unions to ensure that Alun Michael, the Welsh Secretary, became the party's choice to run the assembly in Cardiff .
"This is a recipe for disaster," Trevor Fisher, secretary of Labour Reform, said yesterday. "The desire to present a brand of monolithic unity is beginning to drown out legitimate debate and it is essential that whistleblowers are given protection to air complaints within the party in a proper manner."
Labour Reform is also urging Mr Blair to stick to his long-standing commitment to "one member, one vote" for internal party elections. Many activists refused to campaign in last month's European elections because Labour's candidates were imposed on them. Privately, this criticism is taken seriously by the leadership. "The members felt excluded. In future, we must ensure they are involved," one Millbank source said last night.
Mr Fisher said the failure to use "one member, one vote" to select Labour's candidates was "a major factor in the party's abysmal performance", in the European elections.
He said: "After Millbank selected the candidates centrally, the members simply switched off and did not work. It is essential to restore ownership of the selection process to members, except in very exceptional circumstances... such as by-elections called in emergencies."
Labour Reform is also challenging Mr Blair's new system of party policy- making. The activists want a return to "representative democracy in policy-making".
Ministers claim the new system has allowed 10,000 members to contribute to policy statements on health, welfare and crime. But grassroots critics complain that members have little influence, saying the process is rigged in favour of the leadership.
The critics believe that a review of welfare policy, conceded by ministers when the National Policy Forum met at the weekend, was a device to "kick the issue into the long grass" rather than meeting the demands of activists for a change of direction.Reuse content